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Talk about Adafruit Raspberry Pi® accessories! Please do not ask for Linux support, this is for Adafruit products only! For Raspberry Pi help please visit: http://www.raspberrypi.org/phpBB3/

Hi, I have purchased your Adafruit Blue&White 16x2 LCD+Keypad Kit for Raspberry Pi and have mounted the display only on the pannel of the project that I am building for my Son (Motorised camera slider) with 180mm jumper leads. I also wish to use external switches (see attached photos) to operate the Pi/display so have checked the connections on your board and have found the following1 Select button connections Pad 2 common Pad 42 Left button conections Pad 2 common Pad 33 Up button conections Pad 2 common Pad 34 Down button conections Pad 2 common Pad 45 Right button conections Pad 2 common Pad 3Is the above correct and I only need the two connections on all switches ? could I daisychain the common conections at the switches and only run one wire to Pad 2 for neatness or is it better to run pairs for all buttons.Thanks for your great site and products.

The switches we use for that kit are commonly known as 'tact switches', short for 'tactile'.

There are only two electrical connections on a tact switch. If you hold the switch so the pins come out the left and right sides, the upper two pins are connected to each other, and the lower two pins are connected to each other. The upper and lower pairs of pins have no connection by default, but pressing the switch button creates a connection between them.

A tact switch usually has one pair of pins connected to GND and the other pair connected to what's called a 'pull up resistor'. Ladyada wrote a fantastic tutorial on the subject which can be found here: http://www.ladyada.net/learn/arduino/lesson5.html

You don't have to connect the pull up resistor or GND to both sides of a switch, and it doesn't matter which side you use to make the connections. The extra/redundant pins on a tact switch make life easier for people who have to route traces on PBCs.

In terms of carrying the signals from our PCB to the device you want to use, there are two arguably valid choices:

- For each switch, you can run a pair of wires (pull up and GND) from the appropriate pads on the PCB to the off-board switches.

- For each switch you can run a single wire (the pull up) from the appropriate pad on the PCB to the off-board switch, then you can run a single GND wire from the PCB to the external switches, and daisy-chain the GND connections from one switch to the next.

The first version is a bit pedantic, but technically more correct. The second version has a slightly higher chance of seeing interference between the button signals, but the odds are still very low.

Personally, I'd use the two-wires-per-switch option. I find daisy-chained connections to be more trouble than the wire they save. Either way, you life will be much easier if you use highly flexible wire (which you can get by cutting the ends off of these: http://www.adafruit.com/products/153) and bundle the wires into a harness between the off-board switches and the PCB.

When you void a product warranty, you give up your right to sue the manufacturer if something goes wrong and accept full responsibility for whatever happens next. And then you truly own the product.

Hi, another question on this kit is that I wish to use it on a battery operated unit so I have the desire to turn the display back light on and off on a switch to save power. Can this be achieved by placing the switch in series between one of the resistors ( 220 ohm Blue) leads and its terminalThanks Jon

"When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you" - Pablo Picasso